Guild Wars 2

Achievement Agent of Entropy

It still says 1/200 repeated 24 times and still not complete, what does it take to complete this Achievement?

It never completes. There is a cap of 250 on the number of achievement points you can get from it. If you hover over it you can see how many points you have gotten from it.

After you’ve gotten 250 achievement points, you can still “complete” it, but it does nothing (no achievement points, no experience).